Abstract: The opening up and working smoothly of the Silk Road is impossible without support of oasis, and this support is realized through oasis various functions. Posthouse in oasis should ensure the stream of people and goods going forward in the Silk Road. There must be military and administrative institution to defend city, settle down citizens, and have proper armed force to ensure safety of the Silk Road. Enough food is necessary. Communication, military institution and cultivation promote the appearance of commercial market, which creates large amount of wealth. This wealth consequently provides guarantee to communication, national defense and cultivation. It is just that the mutually operation of posthouse, stationed army, cultivation and commercial market in oasis makes the Silk Road run through in history.